Free Markets should rule. As long as you aren't seeing manipulation to keeping the price high it should be allowed to stay this way.
If a reverse conversion is implemented there should be plenty of warning and there should be a limit on how much can be converted per day. This would avoid a complete crash of the market.
On the flip side if the inverse conversion is allowed I can trade 4000 steem for 24000SBD internally and then buy steem on the open market to then convert again. It actually would allow for a short term massive increase in holdings for those that have liquid steem. It would take some time before the markets evened out and in the mean time massive profits could be made.